Need Help in Primary 6 Maths Qns

[Cerano]

your answer wrong leh....

 

pai seh careless.

 

should be

ken x-16

[Babyt]

initially tried drawing diagram but dunno how to draw also...lol

 

in real life, just call these 2 kids and ask them HOW MUCH U HAVE ;p

 

 

[Wbucket]

That's just a list, formulated decades ago. Study not just his theory, but the research methods behind it and you might find that a lot of observations that he made decades ago about kids and learning don't hold too well this day, and especially in the local context. His observations were mostly made of his own children and the children of highly educated and well off professionals, and this theory does not account for environmental factors. And that's just scratching the tip of the iceberg when it comes to criticisms of his theory. I've had the displeasure of studying his stuff before and somewhat irritated my tutor by asking such questions that nobody could satisfactorily answer. Shows how rigorous this sort of research is.

 

I hope people no longer think that kids generally reach the formal op stage by 12, or even 16. You have to look at his theory in the much wider socioeconomic context of the current generation. In Mathematics, you might want to refer to Van Hiele's theory instead for a more updated view on how people develop reasoning ability - ostensibly it's a study in the learning of geometry, but geometry and algebra are really both sides of the same coin.

 

I think a primary school teacher should not watch a kid struggle with something difficult and abstract like algebra and cite Piaget as an excuse. That's being quite irresponsible. Talk to the kid, try different ways of explaining things, find SOMETHING that works. Nobody knows what that something is, because that's a function of both the teacher, the kid and the material being explained. But that's what teachers are paid to do - teach, and one of the best ways to go about it is to talk and interact with the child (of course, this is being idealistic.. if you're in the profession, then you and I both know why this isn't always possible....) Now that's something from Piaget that I can agree with.

I doubt a smart alec who can cite Piaget's work would have problem with these problems, just maybe attitude problem. Personally I didn't study Piaget's and thus wouldn't know how applicable his theory is. A quick read seems to suggest Van Hiele's theory is about development through proper stages without regard to age, where as Piaget's generalized everything with biological development. Maybe somewhere along the line 2 of these theory do meet.

 

Anyway, these is moving into areas I am not strong in. But I would like to see some of you all work towards reforming our educational system if it is really not satisfactory.

[Ivan96935sg]

Hi guys, got another question to seek guidance on:-

 

Question: A grocer had some mangoes. When he packed them into bags of seven mangoes, he would have 3 mangoes left. When he packed them into bags of nine mangoes, he would be short of 6 mangoes. What was the least number of mangoes that the grocer had?

 

I have tried but failed.......guess my maths is not up to mark. Anyone to share how to enlighten my kid in this problem sums?

[Chewbacca]

Wahlan eh!

 

You guys totally forgotten everything you were taught, didn't you?

[Swingarm]

common multiple of 7 and 9 than add 3

Edited April 14, 2010 by Swingarm

[Joseph22]

Hi guys, got another question to seek guidance on:-

 

Question: A grocer had some mangoes. When he packed them into bags of seven mangoes, he would have 3 mangoes left. When he packed them into bags of nine mangoes, he would be short of 6 mangoes. What was the least number of mangoes that the grocer had?

 

I have tried but failed.......guess my maths is not up to mark. Anyone to share how to enlighten my kid in this problem sums?

 

Bro. you must remember in Pri 6. We had not been taught Algebra yet. We were taught to us diagrame. So do the sum with Diagrame and you can get it. this one very simple

[Swingarm]

nowadays they have been taught algebra... but not advance yet...

[Joseph22]

nowadays they have been taught algebra... but not advance yet...

yeah. but no required to used in PSLE if i am not wrong. Taught to do but not how to used yet. So in PSLE, they are still using diagrame method i think.

 

I ever solve one sum in P4 using Algebra (some how used it by own thinking and not taught before) i was marked down by teacher Anyway that one is in math club i joined rather than in exam...

[Swingarm]

The syllabus have change now... wat i've studied in secondary can be found in p5 or p6

[1fast1]

Hi guys, got another question to seek guidance on:-

 

Question: A grocer had some mangoes. When he packed them into bags of seven mangoes, he would have 3 mangoes left. When he packed them into bags of nine mangoes, he would be short of 6 mangoes. What was the least number of mangoes that the grocer had?

 

I have tried but failed.......guess my maths is not up to mark. Anyone to share how to enlighten my kid in this problem sums?

 

Actually, the problem is poorly stated. I can justify an answer of 3 mangoes, which would mean the grocer had zero bags of 7 each, and 1 bag with six mangoes short. However, I think the answer they're probably looking for is 66 mangoes.

 

As always, I would prefer to do it algebraically. Let the number of bags of seven be x. It then seems intuitive that the grocer would have less bags of nine. Let's say he had k less bags of nine, meaning he had (x - k) bags of nine.

 

Then, equating the total number of mangoes (N),

 

7x + 3 = 9(x-k) - 6 (= N)

 

which simplifies to:

 

2x = 9(k+1)

 

Interesting. The LHS is even, which means k must be odd. We are also trying to minimise x, to get the *least* number of mangoes, so we should also minimise k.

 

Any value of k < -1 would give negative values of x, which would be nonsense. One can actually select k = -1 to get x = 0, which would give the trivial solution I mentioned above with 3 mangoes. However, if the problem is constrained such that the grocer must pack at least one bag of 7 and at least one bag of 9, the smallest value of k is then 1.

 

Which gives: 2x = 18, x = 9. Then the total number of mangoes becomes (by back-substitution),

 

N = 7*9+3 = 66.

 

So he had 9 bags of seven mangoes and 8 bags of nine mangoes.

 

I suspect a more rigorous solution would involve an application of Chinese Remainder Theorem, but I don't expect even our ridiculous Pri. school syllabus to have covered Number Theory to this extent, so this is the best I can do.

Edited April 14, 2010 by Turboflat4

[Vince69]

I need some help on the following Maths Qns which I have trouble explaining to my kid. Anyone kind enough to guide me with the explanation?

 

"If Ken gives Devi $16, he will have the same amount of money as Devi. If Devi gives Ken $20, the amount she has will be 1/10 that of Ken's. How much money does Ken have?"

 

this question is not specific enough

 

loose ends include:

1) "If Devi gives Ken $20, the amount she has will be 1/10 that of Ken's"

By itself, this is alright, but since this was put in after the previous statement, then the question is.... is this statement inclusive of the first statement. The reason is that this will change the equation drastically.

By itself only: (Devi-$20)*10 = Ken+$20

Inclusive of the first statement: ((Devi+$16)-$20)*10 = (Ken-$16)+$20

 

2)"How much money does Ken have?"

Is this refering to what Ken have initially? or at the end of both transactions? the answer will definitely impact the what the answer will be.

 

[The_Bear]

Hi guys, got another question to seek guidance on:-

 

Question: A grocer had some mangoes. When he packed them into bags of seven mangoes, he would have 3 mangoes left. When he packed them into bags of nine mangoes, he would be short of 6 mangoes. What was the least number of mangoes that the grocer had?

 

I have tried but failed.......guess my maths is not up to mark. Anyone to share how to enlighten my kid in this problem sums?

 

I don't really care how many mangoes the grocer has but if the grocer is a FT, I sure gonna check my bag to make sure he gave me 9 mangoes....

[Swingarm]

i prefer 7 really big ones compare to 9 small ones

[Swingarm]

Actually, the problem is poorly stated. I can justify an answer of 3 mangoes, which would mean the grocer had zero bags of 7 each, and 1 bag with six mangoes short. However, I think the answer they're probably looking for is 66 mangoes.

 

As always, I would prefer to do it algebraically. Let the number of bags of seven be x. It then seems intuitive that the grocer would have less bags of nine. Let's say he had k less bags of nine, meaning he had (x - k) bags of nine.

 

Then, equating the total number of mangoes (N),

 

7x + 3 = 9(x-k) - 6 (= N)

 

which simplifies to:

 

2x = 9(k+1)

 

Interesting. The LHS is even, which means k must be odd. We are also trying to minimise x, to get the *least* number of mangoes, so we should also minimise k.

 

Any value of k < -1 would give negative values of x, which would be nonsense. One can actually select k = -1 to get x = 0, which would give the trivial solution I mentioned above with 3 mangoes. However, if the problem is constrained such that the grocer must pack at least one bag of 7 and at least one bag of 9, the smallest value of k is then 1.

 

Which gives: 2x = 18, x = 9. Then the total number of mangoes becomes (by back-substitution),

 

N = 7*9+3 = 66.

 

So he had 9 bags of seven mangoes and 8 bags of nine mangoes.

 

I suspect a more rigorous solution would involve an application of Chinese Remainder Theorem, but I don't expect even our ridiculous Pri. school syllabus to have covered Number Theory to this extent, so this is the best I can do.

 

too chim for a pri 6...

 

 

 

[Ben5266]

Hi guys, got another question to seek guidance on:-

 

Question: A grocer had some mangoes. When he packed them into bags of seven mangoes, he would have 3 mangoes left. When he packed them into bags of nine mangoes, he would be short of 6 mangoes. What was the least number of mangoes that the grocer had?

 

I have tried but failed.......guess my maths is not up to mark. Anyone to share how to enlighten my kid in this problem sums?

Think Swingarm is correct. Answer is 66.

I think the key point here is , when pack 9 in a bag, he would be short of 6. This also means if he pack 1 bag less, he will have 3 left. Same as pack in 7.

So, multiply 7 and 9 gets 63. Plus 3.

[Vince69]

Hi guys, got another question to seek guidance on:-

 

Question: A grocer had some mangoes. When he packed them into bags of seven mangoes, he would have 3 mangoes left. When he packed them into bags of nine mangoes, he would be short of 6 mangoes. What was the least number of mangoes that the grocer had?

 

I have tried but failed.......guess my maths is not up to mark. Anyone to share how to enlighten my kid in this problem sums?

A P3 student will use the draw a table approach...

1bag of 7 + 3 = 10; 10/9 = 1R1 (failed, 8short for 2bag)

2bag of 7 + 3 = 17; 17/9 = 1R7 (failed, 1short for 2bag)

3bag of 7 + 3 = 24; 17/9 = 2R6 (failed, 3short for 3bag)

....... and so on.....

9bag of 7 + 3 = 66; 66/9 = 7R3 (passed, 6short of 10bag)

Edited April 14, 2010 by Vince69

[Tigerwoods]

this question is not specific enough

 

loose ends include:

1) "If Devi gives Ken $20, the amount she has will be 1/10 that of Ken's"

By itself, this is alright, but since this was put in after the previous statement, then the question is.... is this statement inclusive of the first statement. The reason is that this will change the equation drastically.

By itself only: (Devi-$20)*10 = Ken+$20

Inclusive of the first statement: ((Devi+$16)-$20)*10 = (Ken-$16)+$20

 

2)"How much money does Ken have?"

Is this refering to what Ken have initially? or at the end of both transactions? the answer will definitely impact the what the answer will be.

I totally agree with you.

The problem with today's Maths Questions is the Poor sentence construction that is vague at best. Are our kids learning Engrish or Maths ?

My wife and I are struggling to understand many questions - so what can you expect from a 12 yr old ??